1. Field of the Invention
The present invention relates to electronic musical instruments and more particularly to a modular electronic circuit which is capable of duplicating the sound that results from striking a natural percussion instrument or any other short duration sound such a bat impacting a baseball.
2. Description of the Prior Art
U.S. Pat. No. 4,148,240, entitled Percussion Simulating Techniques, issued to Douglas R. Moore and Alberto Kniepkamp on Apr. 10, 1979, teaches an improved electronic musical instrument capable of simulating a sound resulting from the striking of a natural percussion instrument. The electronic instrument includes playable keys, a tone signal generator for generating tone signals and an output circuit for converting the tone signals to audible tones. A control circuit responsive to the depression of any one of the keys enables one or more of the tone signals representing one or more fundamental pitches to be transmitted to the output circuit for a first time period and enables another tone signal representing a pitch nonharmonically related to the fundamental pitches to be transmitted to the output for a second time period less than the first time period. By combining the tone signals corresponding to the fundamental and nonharmonic pitches the sound of a percussion instrument is simulated.
The general nature of the harmonic spectrum of natural percussion instruments, such as a xylophone, bars, bells or chimes, has been known for some time. After a short transient or strike time period resulting from striking a percussion instrument has passed, the instrument generally emits a sustaining tone (which gradually decays) having a fundamental pitch or frequency component, together with harmonic frequency components. However, during the strike time period immediately after the instrument is struck, complex sound waves (i.e., strike tones) having complex frequency spectra are generated. In general, these complex strike tones are nonharmonic; that is, they are non integer multiples of the fundamental frequency produced by the sustaining tone of the instrument.
The electronic musical instrument industry has long sought economical techniques for simulating the sound waves produced by natural percussion instruments, especially the complex transient strike tone produced by the striking of instruments. However, the strike tones are so complex that no economical way of simulating them has been discovered. Complex and costly electronic devices for simulating percussive sounds have been proposed in the past. For example, in a paper entitled, "The Synthesis of Audio Spectra by Means of Frequency Modulation," published in the Journal of the Audio Engineering Society, Volume 27, Number 7, dated Sept. 7, 1973, John Chowning proposes that percussive sounds, such as bells, and chimes can be simulated by frequency modulation circuitry. However, this technique requires complicated frequency modulation equipment, including means for modulating the index of modulation. The frequency modulation equipment is required by Chowning in order to produce the nonharmonic pitches required to simulate the strike tone of a natural percussion instrument.
U.S. Pat. No. 4,135,423, entitled Automatic Rhythm Generator, issued to Glenn M. Gross on Jan. 23, 1979, teaches an automatic rhythm generator of an electrical musical instrument which includes a rhythm pattern generator for rhythmically selecting for actuation different ones of a plurality of instrumentation circuits to be sounded and a strobe pulse generating circuit for establishing the appropriate pulse width of a drive pulse needed by each instrumentation circuit for proper actuation thereof. The rhythm pattern generator circuit selectively enables a plurality of drive gates respectively associated with the plurality of instrumentation circuits during selected ones of a succession of periodic rhythm cycles in accordance with a predetermined rhythm pattern. The strobe circuit is synchronized with the rhythm pattern generator and generates during each rhythm cycle a plurality of strobe pulses on a corresponding plurality of outputs respectively associated with the plurality of instrumentation circuits. Each of the strobe pulses has a width preselected for the instrumentation circuit which it is associated. The enabled drive gates provide a drive pulse to their associated instrumentation circuits in response to, and having a pulse width proportional to that of, the strobe pulse applied thereto.
Automatic rhythm playing or generating systems for use with electronic organs or similar instruments are well known in the art. Examples of such circuits are shown in a large number of U.S. Pat. Nos. including 3,548,065 of Freeman issued Dec. 15, 1970, to Chicago Musical Instrument Co., now Norlin Music, Inc., the assignee of the present application; 3,553,334 of Freeman issued Jan. 5, 1971, to Chicago Musical Instrument Co.; 3,567,838 of Tennes issued Mar. 2, 1971, to Hammond Corporation; 3,760,088 of Nakada issued Sept. 18, 1973, to Nippon Gakki Seizo Kabushika Kaisha; 3,763,305 of Nakada et al., issued Oct. 2, 1973 to Nippon Gakki Seizo Kabushiki, 3,764,722 of Southard issued Oct. 9, 1973, to C. G. Conn Ltd.; and 3,840,691 of Okamoto issued Oct. 8, 1974, to Nippon Gakki Seizo Kabushiki. Reference may be had to these patents for a detailed description of the different types of circuitry and the various techniques by which rhythm signals and tones may be automatically generated.
Briefly, all such circuits employ a plurality of rhythm voice or instrumentation circuits which produce tone signals respectively corresponding to a plurality of different musical instruments and suitable circuitry for actuating preselected ones of the instruments during selected ones of a succession of rhythm cycles. The tempo or rate at which the rhythm cycles are generated is customarily established by an oscillator or rhythm clock which is variable in frequency. In such circuits, different rhythm patterns are selected through means of manually actuateable switches to choose different rhythm patterns such as rhythms for a march, tango, swing, cha-cha, and rock. The different instrumentation circuits simulate different percussion instruments such as blocks, bass drum, brush cymbal, snare drum, etc. or even non-percussion instruments.
Depending upon the rhythm patter selected, none, one or plural instrumentation circuits are actuated during each rhythm cycle. For example, with the rhythm pattern for swing selected, the bass drum and brush instrument circuits may be actuated on the first rhythm cycle, no instruments actuated during the second and third rhythm cycles, the snare drum actauted during the fourth rhythm cycle, no instrument actuated during the fifth rhythm cycle, the brush instrument again actuated on the sixth rhythm cycle and so on in like manner for the next six rhythm cycles.
Each of the instrumentation circuits require a drive pulse applied thereto of appropriate width for proper actuation. Typically, each of the instrumentation circuits comprises a band pass filter having a high Q characteristic that produces an exponentially decaying sine wave on its output having a frequency equal to the resonant frequency of the filter. This sine wave output of each instrumentation circuit is produced when a rectangular wave drive pulse which should be approximately equal to one-fourth the period of the resonant frequency, for a drive pulse of this width when applied to the instrumentation circuit, will result in an output signal of optimum characteristics with regard to amplitude and distortion.
In known automatic rhythm system, drive pulses of suitable width have been provided by means of monostable multivibrators or other suitable pulse shaping circuits. The monostable multivibrators, in turn, are driven by pulses of arbitrary widths without regard to the needs of the instrumentation circuit.
Disadvantageously, such monostable multivibrators and pulse shaping circuits were not readily amenable to embodiment in integrated circuit form together with the other parts of the automatic rhythm generator circuitry. Accordingly, the cost reducing and other benefits derived by providing the entire automatic rhythm generator circuitry in integrated circuit form had not heretofore been obtained until the device of U.S. Pat. No. 4,135,423.
U.S. Pat. No. 4,058,043, entitled Programmable Rhythm Apparatus, issued to Masashi Shibahara on Nov. 15, 1977, teaches a programmable rhythm apparatus for use with an electronic musical instrument which includes a sequential pulse generator, a plurality of individually programmable rhythm channels or tracks each producing an output pulse pattern in response to the sequential pulse generator and a standard voice generation circuit to receive the pulse output pattern from the programmed rhythm channels. The voice generation circuit produces a signal representative of an unpitched instrument with a rhythm pattern corresponding to the pulse output pattern of an individual rhythm channel. The voice generation circuit output signals corresponding to each rhythm channel and representing different unpitched instruments are combined and applied to an audio transducer. Each individual rhythm channel can be programmed by the instrument player to provide a pulse output sequence representative of any rhythm pattern desired. Each rhythm channel has a plurality of logic means and a selection means. The instrument player uses the selection means to set or program various ones of the plurality of logic means to form a pattern corresponding to the desired rhythm. Thereafter, each set logic means produces an output pulse upon receipt of a sequence pulse from the pulse generator. A switching network can be provided between the outputs of the rhythm channels and the input terminals of the voice generation circuit to provide increased flexibility and versatility. Furthermore, the programmable rhythm apparatus can be used in conjunction with the fixed rhythm matrices of the prior art to provide selectable rhythm variation for certain unpitched musical instruments and the standard rhythm for others.
U.S. Pat. No. 4,163,407, entitled Programmable Rhythm Unit, issued to Peter E. Solender on Aug. 7, 1979, teaches a programmable rhythm unit which includes an oscillator which provides a continuous chain of pulses at a predetermined frequency, a circuit which is connected to the oscillator for sequentially and repeatedly arranging the pulses in groups of an equal and predetermined number of pulses corresponding to repeating measures having an equal and predetermined number of beats per measure. The circuit includes a plurality of output lines for receiving the pulses to establish fixed beat positions in each measure, a plurality of rhythm voice input lines, a programmable array for selectively transferring the pulse from selected ones of the output lines to selected ones of the plurality of rhythm voice input lines, and pseudo-randum pulse generator connected to the circuit and to the programmable array for providing a random pulse at a predetermined beat position in each group corresponding to a random beat per measure. The programmable array includes a circuit which selectively transfers the random beat to selected ones of the rhythm voice input lines to establish a programmed rhythm pattern at the rhythm voice input lines. A keyer driver circuit is connected to the rhythm voice input lines, audio signal generator means, and rhythm voicing circuit which is connected to the keyer driver circuit and to the audio signal generator for simulating the audio output of a pluraility of rhythm instruments in accordance with the programmed rhythm pattern.
In all of the above-cited patents the conventional rhythm generator of the prior art which are used in electronic organs produces a sound of a set of percussion instruments which is simulated by one of the following: audio oscillators, envelope generators and tuned resonance circuits. These sounds which are produced by these rhythm generators are close approximations of the actual percussion sounds, but there is much room for improvement.